Abnormal Bowel Loop

Colonic Obstruction

Colon atresia, similar to small bowel atresia, is believed to result from an intrauterine vascular insult. The colon is the least frequent location, representing 5%-15% of all intestinal atresias (Powell and Raffensperger 1982). Multiple atresia syndromes may involve the colon in addition to the small bowel. Proximal location is more common than distal, with atresia beyond the splenic flexure being unusual. Clinical presentation may be delayed up to 48 h after birth. The abdominal scout film, in particular when the atresia is in the ascending colon, is often indistinguishable from obstruction of the distal ileum. The colon proximal to the point of atresia is often massively dilated and a mottled pattern of air and meconium may be identified. Plain film is usually unclear prior to 12-24 h of age so that an adequate amount of air can reach the site of obstruction (Hajivassiliou 2003). Sonography can determine the cause of distension before air is present in the distal bowel. The sonographic features of colon atresia are dilated distal small bowel and proximal colon, which often is markedly echogenic secondary to retained meconium.

Contrast-enema usually reveals a microcolon distal to the atresia, with obstruction to the retrograde flow of barium at the site of the atresia (Fig. 1.29). A "wind-sock" appearance may be observed with membranous atresias (Winters et al. 1992). Calcification of meconium peritonitis due to in utero bowel perforation is present in about 12% of atresia cases, and can be diagnosed antenatally by sonography.

Hirschsprung disease is a form of low intestinal obstruction caused by the absence of normal myenteric ganglion cells in the submucosal and intermuscular myenteric plexuses of a segment of the colon. Clusters of enlarged, unmedullated nerve fibers have taken their place. In normal intrauter-ine development, neuroenteric cells migrate from the neural crest to the upper end of the gastrointestinal tract by 5 weeks and proceed in a caudal direction. These cells reach the rectum by 12 weeks and commence the intramural migration from the myenteric plexus (Auerbach's plexus) to the submucosal plexus (Meissner's plexus). Hirschsprung's disease is caused by abnormal neural crest cell migration resulting in arrested distal migration of these cells (Gershon and Ratcliffe 2004). The length of the aganglionosis is variable but always commences at the lower end of the rectum and extends proximally for a variable distance. In about 80% of cases, the anomaly does not extend beyond the sigmoid (short segment), while in the remainder it extends proximally to involve variable lengths of the colon and may even involve the terminal ileum (long segment). Ultrashort segment disease with aganglionosis essentially limited to the region of the internal sphincter is very rare, as is aganglio-nosis involving the entire alimentary tract (Meier-Ruge et al. 2004; Dasgupta and Langer 2004). In children with Hirschsprung's disease, the absence of ganglion cells results in the failure of the distal intestine to relax normally, peristaltic waves do not pass through the aganglionic segment and there is no normal defecation leading to functional obstruction. The aganglionic segment remains unexpanded and the proximal colon becomes distended and hypertrophied. Hirschsprung's disease is responsible for approximately 15%-20% of cases of neonatal bowel obstruction. Short segment disease is more common in males at a ratio of 4:1. In long segment aganglionosis, male preponderance diminishes to 2.8:1. Gender distribution is almost equal in the cases with extensive involvement (Kleinhaus et al. 1979)

A positive family history is encountered in about 10% of patients with short segment disease and in 25% of patients with total colonic aganglionosis. Hirschsprung's disease is associated with esopha-geal dysmotility syndromes, malrotation and ileal or colonic atresia. Approximately 3% of patients with Down's syndrome have Hirschsprung's disease. The disease has also been associated with other neuro-cristopathies (neuroblastoma, pheochromocytoma, MEN IIA syndrome) and is thought to be related to their common neuroblastic origin (Rescorla et al. 1992). The severity of the symptoms does not depend entirely on the length of the aganglionic segment. Abdominal distension, failure to pass meconium in the first 24 h of life, constipation, and bilious vomiting are the predominant symptoms, with the signs of obstruction appearing within a few days after birth.

Plain abdominal film of infants with this condition is similar to that of other forms of low small bowel obstruction. The abdomen is filled with several distended loops of the colon and the small bowel often with air-fluid levels. The colon is usually difficult to identify accurately, and air is usually absent in the rectum (Fig. 1.30). About 5% of patients may present with pneumoperitoneum a c

Gaseous Distension

Fig. 1.29a-d. Colon atresia. a Supine radiograph shows gaseous distension of bowel. b,c Contrast enema, anteroposterior and lateral views show abnormally small colon (microcolon) with complete obstruction to retrograde flow of contrast material proximal to the middle transverse portion of colon. d Photograph at operation shows a distended colon up to the site of the atresia (arrow) and a microcolon distal to it

Fig. 1.29a-d. Colon atresia. a Supine radiograph shows gaseous distension of bowel. b,c Contrast enema, anteroposterior and lateral views show abnormally small colon (microcolon) with complete obstruction to retrograde flow of contrast material proximal to the middle transverse portion of colon. d Photograph at operation shows a distended colon up to the site of the atresia (arrow) and a microcolon distal to it secondary to perforation (Dasgupta and Langer 2004). Most of these patients have long segment or total colonic aganglionosis. As in all cases of low intestinal obstruction, a contrast enema is needed. Rectal examination should not be performed prior to the enema as this may mask a low-lying transition zone. The enema examination is started with the patient in a lateral position. The catheter should be placed barely within the rectum, so as not to obscure a transition zone. Balloon catheters should never been used as they may obscure a transition zone or even perforate the aganglionic rectum. Although the contrast enema has classically been performed with barium sulphate, currently low-osmolar water-soluble is the preferred contrast medium because of the risk of barium peritonitis a b d c in the event of colonic perforation. There are many signs of Hirschsprung's disease on contrast enema studies. The most important is the transition zone between the normal or relatively narrow agangli-onic segment and the dilated bowel proximal to it, usually in the shape of an inverted cone (Figs. 1.30 and 1.31). This finding is present in about 65% of neonates (Fotter 1998). When this is observed, the examination should be discontinued, especially if barium is being used, as filling of the more proximal dilated bowel beyond the transition zone may lead to impaction. The transition zone may, however, be difficult to see in newborns. In such cases, the rectosigmoid index may be useful (Siegel et al. 1981). Normally, the rectum is 20%-40% larger than the sigmoid in diameter. In Hirschsprung's disease, this ratio may equilibrate or reverse. The pathologic transition zone is usually somewhat more proximal than the radiographic one (Jamieson et al. 2004). Abnormal contractions and irregular peristaltic activity of the aganglionic portion of the colon may be a useful indicator of the disease, occurring in about 20% of infants, and should not suggest mucosal ulceration. Retention of contrast medium at 24 h with colonic distension may be a helpful sign, but is nonspecific, as it can be observed in 60% of patients without Hirschsprung's disease. On the other hand, good evacuation does not rule out the disease (Rosenmeld et al. 1984).

The radiologic diagnosis of total colonic agangli-onosis is much more difficult. Findings may include normal barium enema, short colon of normal caliber, microcolon, rounding of the colonic flexures, or transition zone in the ileum (Fig. 1.32). Clinical suspicion should be heightened in patients presenting with clear signs and symptoms of distal obstruction, in whom the contrast enema does not demonstrate a specific cause (HAyAkAWA et al. 2003). Histological confirmation is obtained by means of rectal biopsy (SolAri et al. 2003).

Enterocolitis is the major cause of death in patients with Hirschsprung's disease, with a mortality rate as high as 30%. The patients may present with diarrhoea, hypovolemia and prostration. Enterocolitis of Hirschsprung's disease can be diagnosed on plain radiograph by the irregular contour of the dilated colonic wall caused by the edema, spasm, and ulceration of the intestinal wall. Patients who present with perforation typically do not have enterocolitis. Enema is contraindicated in patients with suspected enterocolitis because of the possibility of perforation (Vieten and Spicer 2004).

Functional immaturity of the colon is a common cause of neonatal obstruction, particularly in premature infants and in those whose mothers were treated during labor with magnesium preparation or high doses of opiates or other sedatives. The condition has also been encountered in children of diabetic mothers, or children with septicemia, hypo-thyroidism, or hypoglycemia (CoHen 2003). The term includes meconium plug syndrome and small left colon syndrome. Both entities are associated with dysmotility of the colon. The etiology remains unclear, although they are thought to be associated with immature myenteric plexus ganglia (BurgE and Drewett 2004). These infants have difficulty in initiating evacuation, abdominal distension, and sometimes vomiting, but, in general, bowel distension usually is less severe than in organic obstruction. The condition is both diagnosed and treated with contrast material enemas (De BAcker et al. 1999).

In cases of meconium plug syndrome the meco-nium forms a long, thick, snake-like plug, which obstructs the colon. The contrast enema reveals a large meconium plug as a translucent filling defect surrounded by opaque material filling the rectosig-moid, often extending into the descending colon (Fig. 1.33). The contrast medium will sometimes stream around the plug to give a double contrast appearance, with the contrast-lined colonic walls showing up against the negative filling defect of the plug. The large plug is usually evacuated during or soon after the enema examination (Loening-BAucke and KiMurA 1999). Typically, following the enema there is clinical improvement, and over the course of hours to days, radiographic and clinical signs of obstruction subside. The only problem is that a few cases of meconium ileus and a few cases of Hirschsprung's disease may be incorrectly lumped into this group. Then, if the difficulty is not promptly and completely cured a sweat test for cystic fibrosis and further observation for Hirschsprung's disease should be carried out (LeQuesne and ReillY 1975).

The clinical presentation of patients with small left colon syndrome is very similar to that of patients with meconium plug syndrome. Air-fluid levels are often absent in the upright film, particularly prior to 48 h of life. "Soap bubble" meconium is typically seen in the collapsed left colon on the plain film, and the distended bowel tends to be less than that seen in atresias. The contrast enema reveals a normal or slightly dilated colon and rectum but a c

Enema Pain Ache Hirscprungs

Fig. 1.30a-e. Hirschsprung disease. Supine (a), upright (b) and lateral (c) plain radiographs show distension of the bowel corresponding to a low obstruction, with air-fluid levels in the upright film and absence of gas in the rectum in the lateral film. d,e Contrast enema shows a distended colon and an obvious zone of transition (arrows) in the rectosigmoid junction. The caliber of the rectum is very small

Fig. 1.30a-e. Hirschsprung disease. Supine (a), upright (b) and lateral (c) plain radiographs show distension of the bowel corresponding to a low obstruction, with air-fluid levels in the upright film and absence of gas in the rectum in the lateral film. d,e Contrast enema shows a distended colon and an obvious zone of transition (arrows) in the rectosigmoid junction. The caliber of the rectum is very small b a d c a

Pink Sock Inverted Colon

Fig. 1.31a,b. Hirschsprung disease. a Contrast enema shows a distended colon and a small rectum and portion of the colon. The rectosigmoid index is abnormal. b Intraoperative photograph demonstrates the transition zone (arrows) with the shape of an inverted cone b

Fig. 1.31a,b. Hirschsprung disease. a Contrast enema shows a distended colon and a small rectum and portion of the colon. The rectosigmoid index is abnormal. b Intraoperative photograph demonstrates the transition zone (arrows) with the shape of an inverted cone a

Bowel Loop

Fig. 1.32a-d. Total colonic agan-glionosis. a Plain radiograph of the abdomen demonstrates low obstruction. b,c Anteroposterior and lateral views during contrast enema show the shortened colon compared with the normal redundancy of the neonatal colon, with the flexures pulled down and a normal rectosigmoid index. d Intraoperative photograph shows dilated bowel loops with the transition zone at the distal ileum d

Fig. 1.32a-d. Total colonic agan-glionosis. a Plain radiograph of the abdomen demonstrates low obstruction. b,c Anteroposterior and lateral views during contrast enema show the shortened colon compared with the normal redundancy of the neonatal colon, with the flexures pulled down and a normal rectosigmoid index. d Intraoperative photograph shows dilated bowel loops with the transition zone at the distal ileum b a a d the left colon up to the splenic flexure is very small, resembling a microcolon (Fig. 1.34). The amount of meconium present in the colon is variable, and discrete plugs of meconium at the point of transition may or may not be seen (Hajivassiliou 2003). Typically, after the enema, there is clinical improvement, and over the course of hours to days radiographic and clinical signs of obstruction resolve. The only important differential diagnosis in babies with these findings is Hirschsprung's disease with a transition zone at the splenic flexure. There are several findings that can be helpful. The distal rec-tosigmoid colon is of normal caliber and larger than the left colon, the proximal colon is less dilated than in Hirschsprung's disease and the transition zone of small left colon syndrome tends to be quite abrupt, whereas in Hirschsprung's disease it tends to be cone-shaped and gradual. However, the distinction between both entities is not always possible on the basis of radiological findings and a rectal biopsy must then be performed (Amodio et al. 1986; De Backer et al. 1999).

Colon Long Plug

Fig. 1.33a-d. Meconium plug syndrome. Anteroposterior (a) and lateral (b) plain radiographs show distension of bowel loop consistent with low obstruction. c Isosmolar water-soluble contrast enema, lateral view outlines the characteristic long filling defect (arrows) within the colon. d Clinical image of a meconium plug surgically obtained in a patient in whom several attempts to conservatively solve the obstruction failed

Fig. 1.33a-d. Meconium plug syndrome. Anteroposterior (a) and lateral (b) plain radiographs show distension of bowel loop consistent with low obstruction. c Isosmolar water-soluble contrast enema, lateral view outlines the characteristic long filling defect (arrows) within the colon. d Clinical image of a meconium plug surgically obtained in a patient in whom several attempts to conservatively solve the obstruction failed

Rectosigmoid Obstruction

Fig. 1.34. Small left colon syndrome. Isosmolar water-soluble contrast enema in a newborn with low obstruction demonstrates a normal rectum and distal rectosigmoid and a relatively narrow proximal sigmoid and descending colon with a transition to a more dilated colon at the splenic flexure. In 1 week radiographic and clinical signs of obstruction resolved

Fig. 1.34. Small left colon syndrome. Isosmolar water-soluble contrast enema in a newborn with low obstruction demonstrates a normal rectum and distal rectosigmoid and a relatively narrow proximal sigmoid and descending colon with a transition to a more dilated colon at the splenic flexure. In 1 week radiographic and clinical signs of obstruction resolved

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Responses

  • Ireneo
    What is gaseous distention of small bowel loops?
    2 years ago
  • armida
    What is pink sock syndrome?
    3 months ago

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